F.A.A. Lifts Bar on Airport Landing Systems

By RICHARD WITKIN

Published: May 20, 1987

In a move intended to reduce flight delays and increase airport capacity, the Federal Aviation Administration has lifted its five-year-old freeze that prevented airports from installing more electronic guidance systems that allow pilots to land in conditions of low visibility, officials said yesterday.

Lack of precision landing equipment on runways often causes delays in operations when weather falls below minimum requirements for ceiling and visibility. Since some airports have the landing systems on only some of their runways, bad weather can severely reduce an airport's capacity to handle flights.

More than 100 proposed instrument landing systems had been put on hold by the freeze, but the officials said the agency would allow installation of a ''limited'' number of the devices. They emphasized that the agency was sticking to its long-term commitment to install more advanced microwave landing systems, starting in the early 1990's. Persistent Growth in Traffic

The freeze on installation of additional instrument landing systems was imposed in 1982 as a means of expediting the eventual transition to the microwave systems. But in doing so, the freeze deprived airports of landing systems needed to accommodate the the persistent growth in air traffic.

Officials believe that the expansion of the decades-old instrument landing system is handicapped by a shortage of radio frequencies and that the microwave replacements permit much more flexible operations, including runway approaches that take a curved, rather than a straight-in, path.

Current plans to install the microwave systems have drawn strong criticism in Congress because of delays in initial production and questions over how many of the devices are required and how soon they would be needed. A bill is pending before Congress that would order the aviation agency to install some of the older systems. Differences in Equipment

''One of the most serious challenges facing aviation today is limited airport capacity,'' said Donald D. Engen, the Federal Aviation Administrator, in announcing that the freeze was being lifted. He said more instrument landing systems would ''address that problem in the short run,'' while microwave systems would help in the long term.

According to the Transportation Department, both systems ''provide the means to safely guide aircraft to the end of the runway when the pilot cannot see it because of weather conditions.''

In the current version, an invisible electronic path is projected from the runway straight out along the landing approach. By following an instrument on the dashboard, the pilot can maneuver the plane down that path to a safe landing. The instrument constantly indicates whether the plane is too high, too low, or too far to either side.

In the microwave system, the signals are transmitted from the airport in the shape of a wide fan. That permits a variety of curved approaches to the runway and can permit more flexibility in landings. The microwave signals are also considered to be more precise and less prone to frequency congestion. Expected Upsurge in Delays

Mr. Engen, who will retire as head of the aviation agency early his summer, agreed to the policy switch Saturday after it was approved by Transportation Secretary Elizabeth Hanford Dole.

The action comes at the onset of the summer travel season which normally brings an increased number of flights and air-traffic delays. But that problem cannot be eased by the policy change, since it takes from two to four years to install a system.

Airlines and other aircraft operators have pressured Congress to order the agency to install systems on more than a dozen runways. The order, and funds to pay for them, are included in a supplemental appropriations bill that is expected to be approved this summer.

Among the airports with runways on the Congressional list are those in: Anchorage, Baltimore, Charlotte, Chicago, Dallas-Fort Worth, Houston, Nashville, Newark, Portland, Ore., Raleigh-Durham, N.C., Seattle and San Francisco.